As commercially available optical discs, there are CDs (compact discs), on which the recording and reproducing of information is carried out by use of an infrared laser beam with a center wavelength of 0.78 μm, and DVDs (digital versatile discs), on which the recording and reproducing of information is carried out by use of a red laser beam with a center wavelength of 0.65 μm. HD-DVDs and Blu-ray discs, on which the recording and reproducing of information is carried out by use of a blue laser beam with a center wavelength of 0.405 μm, are also starting to become commercially available (HD-DVDs and Blu-ray discs will both be referred to below as ‘blue laser optical discs’ or ‘blue optical discs’).
Recording and reproducing devices for blue laser optical discs are generally structured so that they can also record and reproduce information on conventional DVDs and CDs. As optical pickups suitable for recording and reproducing devices that can record and reproduce information on a plurality of types of optical discs, pickups that can selectively emit laser beams with a plurality of wavelengths have been proposed (see, for example, Patent Documents 1 and 2).
Patent Document 1: Japanese Patent Application Publication No. 2005-339771 (paragraphs 0057-0058, FIG. 3)
Patent Document 2: Japanese Patent Application Publication No. 2002-311219 (paragraphs 0024-0031, FIGS. 1 and 2)